march 18, 2004tips – olivia lupie1 wfc3 filter testing, modeling, designing ghosts (spurious...
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March 18, 2004 Tips – Olivia Lupie 1
WFC3 Filter Testing, Modeling, DesigningWFC3 Filter Testing, Modeling, Designing
Ghosts (spurious reflections) in some UVIS filters were discovered during first ambient calibration of WFC3
Ambient Cal Filter Ghost Characterization – T. Brown, O. Lupie
GSFC Lab Setup (spare and proto-type filters): Randy Telfer (Orbital, GSFC), Ray Boucarut (GSFC)
Filter Modeling: Dave Kubalak, Randy Telfer, (Orbital), Bill Eichhorn (GSFC)
GSFC Lab Data Reduction , Analysis: Sylvia Baggett, Olivia Lupie
Vendors: Barr Associates, Omega Optical
UVIS Ambient Nano Calibration – G. Hartig, N. Reid, S. Baggett, T. Brown, H. Bushouse, B. Hilbert, O. Lupie
TEAMTEAM
March 18, 2004 Tips – Olivia Lupie 2
Parameters Used to Spec a Filter Pre-Install Test
Spectral Requirements
Wavelength tolerances xCentral wavelength xSlopes of bandpass sides/wings xOut of Band Rejection Longward of Passband xOut of Band Rejection Shortward of Passband xRipples in Passband xScattered Light
Angle of Incidence xFocus shift and Filter thickness xAnti Reflection Coatings xOperational Temperature xDimensions
mechanical size, shape xClear Aperture size xWedge - for transmitted wavefront - substrates xOptical Figure xSurface quality
Transmitted Wavefront xScratch-Dig-blemishes xAdhesion of coating xHardness of coating xHumidity xConstruction
Adhesive bondline xCoating materials - general xAdhesives xEdge Sealants xEnvironmental Requirements x not usually tested before install -instrument specific, costly, schedule prohibitive
Parameters Used to Spec a Filter to Vendors
Vendor uses specs to design a filter:•Determine substrates, coatings, coating thicknesses, deposition process.•Provide model of throughput, out of band rejection, spatial uniformity•Model is accepted or rejected•Vendor builds the filter
March 18, 2004 Tips – Olivia Lupie 3
57.3 mm
UVIS CCDUVIS CCDFilter WheelFilter Wheel11
Filter WheelFilter Wheel66
Filter WheelFilter Wheel1212
Edge Rays DefineEdge Rays DefineField-Of-ViewField-Of-View
ImageImageImage RaysImage RaysInstantaneous BeamInstantaneous BeamFootprintFootprint
14 m
m
10 m
m
~3o
WFPC-1’s SOFA – 12 wheels • Converging instantaneous beam footprint • F31 beam• +/- 3 degree range for field angles
WFC3 Filter Testing, Modeling, DesigningWFC3 Filter Testing, Modeling, Designing
March 18, 2004 Tips – Olivia Lupie 4
F225 Transmission Theoretical vs Measured
0
0.1
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1.1
150 200 250 300 350 400 450 500 550 600
Wavelength (nm)
Tra
nsm
issio
n
sht1
desired bandshape
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150 200 250 300 350 400 450 500 550 600
Wavelength (nm)
Tra
nsm
issio
n
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sht2
desired bandshape
Theoretical Transmission
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150 200 250 300 350 400 450 500 550 600
Wavelength (nm)
"T
ran
sm
issio
n"
sht1
sht2
AR Coating
met block
desired bandshape
March 18, 2004 Tips – Olivia Lupie 5
Theoretical Reflectivity
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150 200 250 300 350 400 450 500 550 600
Wavelength (nm)
Refl
ecti
vit
y
sht1 refl
sht2 refl
AR Coat
met block refl
Theoretical Transmission
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150 200 250 300 350 400 450 500 550 600
Wavelength (nm)
"T
ran
sm
issio
n"
sht1
sht2
AR Coating
met block
desired bandshape
Spectral Shaping of the FilterSpectral Shaping of the Filter
March 18, 2004 Tips – Olivia Lupie 6
Modeling Status
11
22
33
44
Anti-reflectionAnti-reflection
Shortpass 1Shortpass 1
Substrate #1
Metal blocker(aberrations –astigmatism)
Substrate #2
Shortpass 2Shortpass 2
Transmitted1st order ghostsaberrated
2nd order ghostsdoubly aberrated
Possible Model of F225W Ghosting (modelers: Randy Telfer, Dave Kubalak)
Aberrations result from reflections from metal blocker
Substrate 1.1 mm
GAP (0.38 mm)
Substrate 3.0 mm
Bond &Spacer
Air-GapConstruction
Ideally – all surfacesperfectly parallel
Airgap replaced adhesive – adhesive reduced throughput and introducemajor spatial dependence across filter
March 18, 2004 Tips – Olivia Lupie 7
F218W
F218W
F225W
F225W
F300X
F606X
<1% in white light<1% in white light
<1% in white light<1% in white light> 10% in white light> 10% in white light > 10% in white light> 10% in white light
(analysis T. Brown with ICAL team)
Flight Filter Ghosts (worst cases)
Some wide band UV air-gap filters exhibited large amplitude ghost images:
March 18, 2004 Tips – Olivia Lupie 8
Faint pointghosts at~0.1% of theprimary imageintensity, moving little with fieldposition.Larger donutghosts at 0.3%,movingsignificantly.
0.02%0.3%
0.06%0.08%
0.13%
0.08%test artifact
Flight – F606W in WFC3White light – 5 micron fiber
Faint pointghosts at~0.01% of theprimary imageIntensity. Fieldangle check inwork..*white lightghosts 10xfainter than Flight – however more testing is needed to verify.
Spare – F606W – labCohu, 10 micron fiberXenon Lamp
Lab Measurements of Spare F606
March 18, 2004 Tips – Olivia Lupie 9
From Nano-Cal :First Order Ghost Strength as a Percentage of Primary Image F225W
0%
10%
20%
30%
40%
50%
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180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500
Wavelength (nm)
Tran
smis
sion
Ratio: Measured ghost flux/prime fluxMeasured
Filter Throughput
strong ghost surfaces 4- 2
strong ghost surfaces 4- 3
strong ghost surfaces 3- 2From Models:
200 nm
400 nm
275 nm
1100 nm
F225W
Primary images ghosts
Low level ghosts
March 18, 2004 Tips – Olivia Lupie 10
First Order Ghost Strength as a Percentage of Primary Image F225W
0%
10%
20%
30%
40%
50%
60%
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80%
180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600
Wavelength (nm)
Tra
ns
mis
sio
n
Surfaces (3-2)
Surfaces (4-3)
Surfaces (4-2)
Surfaces (4-1)
meas ghost ratio
meas trans
Surface (3-1)
Surface (2-1)
Note - Surface (4-2)curve overlaps withextended wing of in band transmission
F225
Model Transmission after two reflections. Tocompare models to measured ratio of ghost strength to in-band transmission (black curve with open circles), scale surface curves by transmission (wfc3 + filter + ota + stimulus) at the wavelength. Models do not yet produce as higha ghost transmission ecause of complexities but they indicate which surfaces are most responsible.
Spectral Modeling of Ghosts (D. Kubalak)Spectral Modeling of Ghosts (D. Kubalak)
Ghost spectral modeling- D. Kubalak
March 18, 2004 Tips – Olivia Lupie 11
Phase Retrieval and Spectral Ghost ModelsPhase Retrieval and Spectral Ghost Models Flight FilterFlight Filter
Phase Retrieval from Focus Sweeps(R. Telfer)
Strange Morphology combination of Astigmatism, overall curvature, local surface ripples
March 18, 2004 Tips – Olivia Lupie 12
Two-surface reflection modeling indicates the metal blocker is the likely origin of the ghost behavior. Vendors also say that the metal coating is the least “controllable”.
The observed wavelength dependence is understood. Red and Blue near-band wings are not as steep as desired. This excess light occurs at the wavelengths where ghosts could be produced by the air-gap construction. Model ghost fluxes (10-12%) are comparable to measured in white light.
Phase Retrieval reveals ghost images are astigmatic for 218W and 225W, that the coatings are tilted w/r to one another, and filter has a slow, slight curvature possibly consistent with a shrinkage/distortion at the spacer/metal blocker interface.
None of these issues have any effect on the transmitted beam and throughput – both were excellent.
Air-Gap Ghost Mechanisms
March 18, 2004 Tips – Olivia Lupie 13
Status Filter-Ghost Mitigation Plan
1. Adopt a 3-option approach for Air-Gaps:
Barr to proto-type new F218, 225, (and 300X) filters – single substrate
IPT tested image quality using special lab setup – flightSpare filters to see if they exhibit less ghosting.
IPT is investigating a wedge fix – original design butwith increased wedge to deflect reflected light;
IPT is investigating dual-wheel air gap – achieved wedge by stacked-SOFA wheel approach;requires two coated substrates and loss of a filter(s).
2. Mechanism for F606w (laminated) ghosts is being discussed with OMEGA.
Barr sent thin prototype single substrate – testing in the GSFC – only one ghost present, white light 0.6%
F218 and F225 spares same problem.F606 spare exhibits similar type ghosts butgreatly reduced ghost amplitude (~0.03%)
Modeling shows you cannot tilt filter enough and still stay with bounds of the filter housing..
By “tilting” the spare air-gap, we can determinehow much relative tilt of the two substratesis needed to move the ghosts out of the fov.Data taken last night.
OMEGA is devising a new design.
STATUSPLAN
March 18, 2004 Tips – Olivia Lupie 14
Off-axisParabola
Filter CCD
Fiber
F/31Beam
Castle CartCastle Cart
DoubleMonochrometer
•UV Sensitive CCD.
•Cover Structure for uniform/dark background.
•Mechanical stage mount for filters.
•Automated Castle and CCD data take system.
•Semi-Automated data reduction and analysis.
GSFC Lab Testing Facility
Goals – last few weeks: 1) Prove that the GSFC Lab Test setup accurately simulates the WFC3, i.e., measurements are true representations of the filter imaging quality, and 2) Measure the flight spares.
Optics Team: R. Telfer, R. Boucarut, D. Kubalak, B. Eichhorn, J. Kirk, B. GreeleyScience IPT: O. Lupie, S. Baggett, B. Hilbert, T. Brown, G. Hartig
presents F31 light beamto the filters as they wouldsee in the WFC3+OTA
March 18, 2004 Tips – Olivia Lupie 15
SPARE F225Cohu Video CCD,200 micron fiber
FLIGHT F2255 micron fiber,WFC3
10%
0.5%
Saturated prime
10%
Saturated prime
(sum ghosts=15%)
UV00
UV14
Lab Measurements of Spare F225W
Note – rotation and stretch are different.
SPARE F225SBIG CCD,10 micron fiber,
UV00UV14
Saturated prime
9%
2%
0.5%
Relative positions and fluxes of ghosts in the spares are comparable to those in the flight similar mechanisms.
March 18, 2004 Tips – Olivia Lupie 16
Example Monochromatic Results for Spare F225W
220nm
Spare F225, SBIG-CCD, 200 micron fiber, 13nm bandpass, double UVIS, ,with ND1 (removed in later imaging).
240nm 260nm 280nm
300 nm 320 nm 340 nm
Figure from S.Baggett
March 18, 2004 Tips – Olivia Lupie 17
Ran many tests to establish sensitivity to ghosts, setup alignment accuracy, and experimented with several different filter orientations: rotation, back to front, tilts, translation, wedge orientation and detector tilts.
nominal
-1d
+1d
-2d
+2d
Establish Setup Sensitivity and RepeatabilityEstablish Setup Sensitivity and Repeatability
Rotate Filter a few degrees from nominal and compareGhost morphology
Xenon Lamp, 10 mic Fiber
Spare F225W
March 18, 2004 Tips – Olivia Lupie 18
Primary, Secondary ghosts emerge from behind the primary andeach other when large translations or rotations of the filter are introduced:ie different locations on filter and differing field angles.
center
+0.5 in
-0.5 in
+1.0 in
-1.0 in
v. Large tilt –30 deg to corner
saturated unsaturated saturated unsaturated
center - shows repeatability
Establish Setup Sensitivity and RepeatabilityEstablish Setup Sensitivity and RepeatabilityAlso Helps modelers to see all the ghostsAlso Helps modelers to see all the ghosts
Translating the filter
Xenon Lamp, 10 mic Fiber
Figure from S.Baggett
March 18, 2004 Tips – Olivia Lupie 19
Prototype F225 – Single SubstratePrototype F225 – Single Substrate
Prototype Single Substrate – large tilts(Xenon Lamp, 10 micron fiber, CCD SBIG)
nominal -3d -6d
-9d -12d -15d
Prototype thickness is smaller than that of a flight filter. Thicker filters result in ghosts at a larger radial distance from the primary.
But tilting the thin filter, we can see when the ghost emerges and use a simpleModel to derive the ghost position with a thicker filter.
Setup artifact
Ghost 0.6%
Figure from S.Baggett
March 18, 2004 Tips – Olivia Lupie 20
"Feb_19 Trial F225W"
0.0E+00
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"Wavelength"
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issio
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th trans
th refl
flight 225-302 trans
orig theor
Feb_19 Trial F225W" - OOB Blocking
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"Wavelength"
Tra
nsm
issio
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theoretical trans
meas 225-302 OOB
ProtoTypeF225FromBarr
March 18, 2004 Tips – Olivia Lupie 21
Prototype F225 – Single SubstratePrototype F225 – Single Substrate
Ghosts as a function of wavelength
SetupSBIG CCD, 200 mic fiberCastle Modes<250nm double UV250-310 double UVIS310-760 double VIS>760 double IR
Setup artifact
Ghost#1Ghost#2
200nm 225nm 250nm 300nm
350nm 400nm 450nm 500nm
600nm
800nm
650nm
850nm
700nm
900nm
750nm
900nm
Figure from S.Baggett
March 18, 2004 Tips – Olivia Lupie 22
March 18, 2004 Tips – Olivia Lupie 23
• 53 of 63 filters exhibit excellent performance, consistent with spec.
• 47 filters < 0.2% ghosts• 6 filters 0.2-0.5% ghosts - multi-substrate - 410M, 689M, 814M - air-gap – 656N, 665N, 673N
• 2 filters 0.7% ghosts: • single substrate+Al blocker - 275W can calibrate• air-gap - 658N
• 2 UV high priority air-gap (with Aluminum blocker) 10-15% ghosts - 218W, 225W unsuitable for flight
• 1 UV air-gap 1% with strange morphology - 300X marginal, tough to calibrate
• 1 3-substr laminated, < 0.5% “point-like” ghosts - 606W most used filter, concern (other filters with very low level “point ghosts”: 625W, 775W, 410M, 467M, 547M, 621M, 689M)
• 1 UV single subst.+Al block, possible surface flaw – 280N serious but low priority filter
• 2 UV Quad filters single substrate, 5% ghosts:– 232N, 243N low priority filters, can calibrate
• Grism – data reduction in work
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